Spatial and temporal distribution of Gymnorhamphichthys rondoni (Gymnotiformes: Rhamphichthyidae) in a long-term study of an Amazonian terra firme stream, Leticia - Colombia

Carolina Escamilla-Pinilla,José Iván Mojica,Jorge Molina

doi:10.1590/1982-0224-20190006

Carolina Escamilla-Pinilla, José Iván Mojica + Show 1 more

Open Access

https://doi.org/10.1590/1982-0224-20190006

Copy DOI

Abstract

ABSTRACT Weakly electric fishes continually emit electric organ discharges (EOD) as a means of communication and localization of objects in their surroundings. Depending on water conductivity, the amplitude of the electric field generated is known to increase with decreases in electrical conductivity of the water. In Amazonian terra firme streams, water conductivity is extremely low and fluctuates constantly due to local and regional rains. In this context, the space between freely moving weakly electric fishes may be expected to decrease, on average, with an increase in water conductivity. To test this hypothesis, we recorded the positions at rest of the sand-dwelling fish Gymnorhamphichthys rondoni in a terra firme stream for several days in alternating months, over two years. Based on daily nearest neighbor distances among individual fish in a grid, we found a uniform temporal distribution pattern (which was not affected by water conductivity) indicative of site fidelity. Here we highlight the role of other factors that could influence resting site fidelity.

Highlights

South American gymnotiforms produce self-generated weak electrical signals in the form of stereotyped electric organ discharges (EODs)
Average monthly numbers of Gymnorhamphichthys rondoni individuals found within the sampling grid and average water conductivity recorded in Yahuarcaca terra firme stream in Leticia, Amazonas
Our two-year field survey of a stable population of freely moving Gymnorhamphichthys rondoni reported a uniform temporal distribution pattern, with water conductivity playing no role in its nearest-neighbor distance

Summary

Introduction

South American gymnotiforms produce self-generated weak electrical signals in the form of stereotyped electric organ discharges (EODs). These are used to communicate agonistic behavior, sexual, and physiological state (Silva et al, 2007), and to locate external objects (Caputi, 2017). EODs are continually emitted by these fish when they are at rest and when they become more active at night. These EOD signals can be detected and recorded in their natural habitats using a custom electric fish finder (Crampton et al, 2007), and the pulse rate recorded as mp files with an audio recorder.

Objectives

Methods

Results

Conclusion